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Physical
Peripheral Nervous System
The peripheral nervous system is the network of nerves and ganglia outside the brain and spinal cord that links them to the limbs and organs.
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The idea
The peripheral nervous system, or PNS, is one of the two parts of the nervous system. The other part is the central nervous system, or CNS, which is the brain and spinal cord. The PNS is made of nerves and of clusters of nerve cells called ganglia, all lying outside the brain and spinal cord. Its main job is to connect the brain and spinal cord to the limbs and organs, relaying messages back and forth.
Sensory nerves carry information, such as touch, pain and temperature, from the body to the central nervous system. Motor nerves carry commands the other way, telling muscles to move and glands to release substances. The PNS has two main divisions, the somatic division and the autonomic division, and each one has a sensory part and a motor part. The somatic division handles movements you choose to make, such as lifting your arm. The autonomic division works without conscious control, managing smooth muscle and glands.
Unlike the brain and spinal cord, the PNS is not shielded by the skull and backbone. It also lacks the blood-brain barrier, which keeps germs and toxins in the blood away from the brain. This leaves the PNS more open to harm.
Check yourself
Question 1 of 3
What are clusters of nerve cells that lie outside the brain and spinal cord called?
Composition
what it's made of
- Nerves — Bundles of nerve fibers that carry signals between the central nervous system and the rest of the body.
- Ganglia — Clusters of nerve cell bodies that lie outside the brain and spinal cord.
- Somatic division — The part that carries sensations from the skin and commands to the muscles you move on purpose.
- Autonomic division — The part that controls smooth muscle and glands without conscious effort.
- Sensory and motor parts — Each division has a sensory part that carries signals in and a motor part that carries commands out.
Connection
how it relates
Under Nervous System
Change
how and why it evolves
- Past
- In a vertebrate embryo, the first sign of the nervous system is a thin strip of cells along the back called the neural plate. Its inner part later becomes the CNS, and its outer part becomes the PNS. Scientists sort nerves partly by how they form as the body develops. Because the optic nerve and retina grow out from the brain, they are grouped with the CNS instead of the PNS.
- Now
- Doctors treat many PNS problems, such as nerve damage from injuries or diabetes. Damaged peripheral nerves can sometimes slowly regrow, which most of the CNS cannot do.
- Next
- Research on nerve repair and on devices that connect to peripheral nerves, such as advanced artificial limbs, may help more people regain movement and feeling.